docs: def validate_statusline(self, valid_statusline):
          """
          Check that the statusline is valid, eg. starts with a numeric
          code. If not, replace with passed in valid_statusline
          """
          code = self.get_statuscode()
          try:
              code = int(code)
              assert(code > 0)
              return True
          except(ValueError, AssertionError):
              self.statusline = valid_statusline
              return False